According to Tom Geoghegan BBC News Magazine, a study of 10,000 US residents showed that those who had the most friends at school made the most money later on — each extra friend added 2% in salary (we assume "extra" here means friends above the average number, but we still wouldn't want to be someone's "extra friend"). The average person apparently has about 150 friends — anthropologist Robin Dunbar says this is "the number of people that you know as persons and you know how they fit into your social world and they know how you fit into theirs." Geoghegan says, "it may sound like a lot, but think of your Christmas card list - 50 cards to 50 couples = 100 friends," thus assuming that we are 1) very popular and 2) very organized and 3) for some reason uninterested in single people.

Geoghegan breaks this group of 150 down further, writing,

They usually consist of an inner circle of five "core" people and an additional layer of 10, he says. That makes 15 people - some will probably be family members - who are your central group and then outside that, there's another 35 in the next circle and another 100 on the outside.

He says the limit for close friends is probably between six and 12, and tells the story of one man who told a woman "he had no vacancies for friends," then sent her a card six months later notifying her of an opening. All this is interesting, but the explicit linkage of friendship and wealth, along with the carefully quantified tiers of friendship, makes a person's relationships with other people sound like an investment portfolio. This outlook encourages people to see friendship in terms of what people can do for them, rather than as a good thing for its own sake. And these days, isn't it more comforting to think of friendship as one thing that doesn't have to do with money?